We recently discovered a zinc-binding compound in human milk which is not present in cow's milk, and presented some evidence that it enhances absorption of zinc in the neonatal period. The goal of this research is to determine the importance of this material in the zinc nutritton of the neonate. This objective will be approached through purification of the zinc binding ligand (ZBI), and its chemical and biophysical characterization. In addition, the role of the ZBL in neonatal absorption of zinc will be investigated through the development of a radioimmunoassay for the ZBL and its quantification, and by fluroescent antibody studies of ZBL in the intestine of the young rat. The proposed research is highly significant for infant nutrition, since considerable evidence indicates that marginal zinc deficiency is a problem in American (formula-fed) infants. In addition, fundamental information on mechanisms of zinc absorption and their development in the newborn may be developed.